Voice Quality
Monitoring

To
measure the voice quality of calls that are sent and received within the
network, Cisco IP Phones use these statistical metrics that are based on
concealment events. The DSP plays concealment frames to mask frame loss in the
voice packet stream.

Concealment Ratio metrics—Show the ratio of concealment frames over total speech frames. An interval conceal ratio is calculated
every 3 seconds.

Concealed Second metrics—Show the number of seconds in which the DSP plays concealment frames due to lost frames. A severely
"concealed second" is a second in which the DSP plays more than five percent concealment frames.

Note

Concealment
ratio and concealment seconds are primary measurements based on frame loss. A
Conceal Ratio of zero indicates that the IP network is delivering frames and
packets on time with no loss.

You can
access voice quality metrics from the Cisco IP Phone using the Call Statistics
screen or remotely by using Streaming Statistics.

Average MOS LQK decreases may indicate widespread and uniform impairment.

Individual MOS LQK decreases may indicate bursty impairment.

Cross-check the conceal ratio and conceal seconds for evidence of packet loss and jitter.

MOS LQK scores increase significantly

Check to see if the phone is using a different codec than expected (RxType and TxType).

Check to see if the MOS LQK version changed after a firmware upgrade.

Note

Voice quality metrics do not account for noise or distortion, only frame loss.

Cisco IP Phone Cleaning

To clean your Cisco IP Phone, use only a dry soft
cloth to gently wipe the phone and the phone screen. Do not apply liquids or
powders directly to the phone. As with all non-weatherproof electronics,
liquids and powders can damage the components and cause failures.

When the phone is in sleep mode, the screen is blank and
the
Select button is not lit. When the phone is in
this condition, you can clean the screen, as long as you know that the phone
will remain asleep until after you finish cleaning.